The saga of attempting to improve the effectiveness of the average infantryman continues today. Now it’s the turn of the Americans. In the late 1990s, the US Military wanted to try to replace the M-16. Again. And the conclusion of the experts was that bullet-launching technology had peaked with the M-16, and there weren’t any good ways to improve it further. So more lethality would have to come elsewhere.

Considering the problem of an enemy behind cover, the committee decided that the right answer was to have some kind of man-portable airburst munition. And this led to the design of the XM-29 OICW.¹

The XM-29 had three components. The critical one was the grenade launcher. It was a bullpup-looking affair, firing 20mm grenades from a six-round detachable box magazine. These were quite a bit smaller than everyone’s favorite 40 mm grenades, so as to be workable in a magazine, but there still weren’t many of them. Which led to the second component–the “KE Module”, which was a 5.56 carbine made by HK. It had a conventional configuration, and only an 8″ barrel. Further complicating things, the one trigger on the carbine had to also work the grenade launcher, but you had to be able to separate the two modules and use them individually (after a trigger unit was added to the grenade launcher. Plus, there was a massive thermal sight/laser rangefinder/fire control computer unit on top to coordinate the airburst over the head of the enemy. The idea was that the operator would use the rangefinder to determine range, manually program in the distance for airburst, and then fire a grenade.

Unsurprisingly, the result was big, heavy, and very expensive. Fully loaded, the XM29 weighed 8.2 kg, or a hair over 18 pounds. That’s ridiculous. It was big and unwieldy. Oh, and did I mention the cost? The XM-29 was projected to costvover $10,000 per unit. Plus, airburst grenades are roughly ten times as expensive as regular, contact-fused grenades.

All this might be forgiven if it worked. It didn’t. Oh, the carbine bit fired ok. But there were tons of problems with the airburst mechanism. And when it worked, it was judged insufficiently lethal. The 20mm round created fragments that were too small, there was insufficient explosive for a very large kill radius, and a whole bunch of fragments and energy are going to be directed upwards, away from the target. I can’t imagine that it would have been all that combat effective to have to manually program in airburst distances when enemies were firing back either.

After dumping a whole bunch of money into the airburst 20mm rounds, it was finally decided that they were unworkable. The only way to get sufficient lethality was to up the caliber. 25mm was settled on, but this would mean an even bigger grenade launcher unit. Between the ballooning weight and rapidly escalating cost, the project was terminated, and split into the XM-25 (which I’ve talked about here) and the XM-8 carbine (which I’ll talk about later).

So that’s the overview. What do we think of this project? Well, the basic concept might be sound, since I’m all in favor of raining death upon my enemies, but the execution is terrible. It would be much better if the grenade module could attach to an existing rifle to reduce costs, like the Korean K11 program. This also uses a 20 mm grenade module though, and I share the US Army’s concerns about inadequate killing capability of the 20 mm grenades.² The 25 mm grenades of the XM-25 are more effective, and a 25 mm launcher is far too big to mount on a rifle.

An even better solution would be to get airburst 40 mm grenades. There, the launchers and the grenades are already in the system. Lethality has already been proven, and there’s already cheap grenades in the system. You simply have to work out the guidance and fusing, but you’d have to do that anyway with an XM29-type weapon.

Verdict: Funding Denied by Borgundy War Department Ordnance Procurement Board

1.) Objective Individual Combat Weapon. They chose the stupidest name they could.
2.) I have no idea if the South Koreans are satisfied with the performance of the 20 mm, or if they’re banking on the enemy being unarmored, malnourished North Koreans who are also easily frightened or something.